1. Field of the Invention
The present invention relates to an improvement in efficiency of receiving and transferring photoelectrons generated in a photoelectric conversion element of a solid-state image sensing device.
2. Description of the Related Art
Known conventional applications of solid-state image sensing devices include technologies using a time-of-flight (TOF) method for measuring a distance to a target object in a contactless manner. In one known technology using the TOF method, photoelectrons generated in one photoelectric conversion element are allocated to, accumulated in, and read from a plurality of photoelectron hold units. In Ryohei Miyagawa and Takeo Kanade, “CCD-Based Range-Finding Sensor”, IEEE Transactions on Electron Devices, Vol. 44, No. 10, October 1997, pp. 1648-1652 and Ryohei Miyagawa and Takeo Kanade, ITE Technical, Vol. 19, No. 65, pp. 37-41 (November 1995), a pulsed light is emitted from a light-emitting device in an emission period and is not emitted therefrom in an emission stop period, the light-emitting device is driven at a duty ratio of 50% while repeating the emission period and the emission stop period with the same time length, the shutter of the photoelectric conversion element is controlled in synchronism with the emission period and the emission stop period, and thus generated photoelectrons are distributed in two directions. The distance to the target object is measured using the photoelectrons distributed in the two directions. In addition, in Japanese Laid-Open Patent Publication No. 2010-032425, the photoelectrons generated in the photoelectric conversion element are distributed in four directions.